Elimination of Ischemic Mitral Regurgitation Does Not Alter Long-Term Left Ventricular Remodeling in the Ovine Model

Background. The efficacy of annuloplasty for ischemic mitral regurgitation (IMR) has been difficult to establish. Using an established ovine model of IMR, we tested the ability of ring annuloplasty to durably relieve IMR and reverse or limit progression of left ventricular (LV) remodeling during a clinically relevant follow-up period. Methods. A posterolateral infarction known to result in chronic IMR was initiated in 33 sheep. Echocardiography was used to assess LV end diastolic and systolic volumes and IMR (0 to 4 scale) before and 8 weeks after infarction. Eight weeks after infarction, 20 surviving animals with >= 2+ IMR were randomized (1: 1) to no treatment or undersized, semirigid, complete ring annuloplasty placement. LV remodeling and IMR were assessed at 4 and 6 months after infarction. Results. All animals had similarly sized LV volumes at baseline (end systolic, 27.8 +/- 4.6 mL; end diastolic, 53.5 +/- 6.4 mL). The 20 randomized animals survived to complete the study. The degree of IMR before randomization was similar in treatment (2.6 +/- 0.4) and control (2.8 +/- 0.3) groups. At the 6-month follow-up, the degree of IMR was significantly less in the annuloplasty group (0.3 +/- 0.1 vs 3.4 +/- 0.6); however, LV volumes in the treatment group were not significantly different from the control group (end systolic, 82.1 +/- 15.6 vs 81.1 +/- 8.6 mL; end diastolic, 110.4 +/- 22.1 vs 111.1 +/- 16.5 mL). Conclusions. In a clinically relevant ovine model of IMR, annuloplasty provides durable relief from IMR during an extended follow-up period but does not significantly influence LV remodeling.